The present invention relates to a compact carrier package and fabrication method thereof that uses a battery coin cell for carrying an integrated circuit (IC), e.g., "chip".
Currently, there is an ongoing trend toward miniaturization of circuitry and packaging to hold the circuitry. Packaging with a portable power source is a natural progression of the technology. For example, it is desirable to package a chip with a battery for "smart cards" and other security products, cardboard or plastic packaging used to create low cost active displays, portable calculators, watches, toys, and numerous other electronic devices that use so-called "coin cell" or "button" batteries.
A coin cell battery generally refers to a battery with a wafer-shaped housing with conductive leads for powering a chip. The housing is usually plated with nickel or other metal.
An IC may be provided in a micro-module, which is plug-in, miniature circuit composed of micro-elements such as resistors, capacitors, and/or transistors. In a smart card implementation, for example, the micro-module is carried within a cavity of a plastic card body. Conventional contact micro-module technology for smart cards has flush mounted contacts on a chip carrier package. The package is required to get power from a host, and is delivered typically as 5 volts on a contact of the package. Such contacts may be referred to as "ISO contacts" when conforming to standards of the International Standards Organization.
Conventional radio-frequency (RF) micro-module technology has an antenna in the body of a smart card or RF ID package to couple power into the chip package. The chip is able to bi-directionally communicate through the antenna as well.
Batteries have been used in connection with the RF micro-modules to reduce or eliminate the required electromagnetic field strength needed make them operate. Calculators, including buttons, a keypad, an LCD, and a piezo-electric speaker have also been mounted in smart cards with internal batteries. In all of these uses, the batteries have typically been lithium foil or flat cell technology. The batteries are fabricated into either plastic card cavities, or sandwiched into multi-layer boards. The chip or circuitry is typically connected through traces or wires with either a solder or spot weld connection made to the battery itself.
However, several problems arise with the conventional battery-chip packaging technology. For example, lithium foil or flat cell batteries have problems at elevated temperatures, e.g., in an automobile on a hot day, a set-top television/data converter box (e.g., decoder), or a television set. In fact, the battery can fail after only a few weeks of exposure to extreme temperatures. Coin cells, on the other hand, have superior mechanical properties allowing for better behavior at extended high temperatures.
Accordingly, it would be desirable to find a way to use temperature-resistant coin cells in tight form factor devices such as smart cards, and to make easier and more reliable connections to the chip carrier package and other devices.
Additionally, due to the constant drive for miniaturization of electronic devices, it would be desirable to have a compact chip carrier and battery package.
It would further be desirable to have a flexible structure for housing a chip with a relatively large die size, e.g., greater than 25 mm.sup.2.
Moreover, it would be desirable to have a structure for securing a chip that takes advantage of the lower cost and greater availability of coin cells relative to lithium foils or flat cells.
It would further be desirable to have a structure that does not experience "plastic creep" as a failure mode. Conventional holders for batteries can experience plastic creep, thereby potentially causing the battery connection to fail over long time periods.
The structure should also be easy and inexpensive to manufacture, and should protect the chip from dust, moisture, and impacts.
The present invention provides a carrier package for a chip, and a corresponding method, having the above and other advantages.